This invention relates generally to apparatus for material distribution, and more particularly to a discharge apparatus for use in an airlock discharge assembly. The invention further relates to an airlock discharge assembly including an improved discharge apparatus.
Conventional airlock discharge assemblies are currently used for discharging bulk material from a bulk material discharge assembly. The airlock discharge assemblies frequently entrain the bulk material in a fluid such as air for distribution.
FIG. 1 illustrates one conventional airlock discharge assembly 100 including an airlock 102 and a discharge apparatus 120. The airlock 102 includes a rotor 103 for rotation inside a housing 105. The rotor 103 comprises an axle 104 having an axis 107, a hub 106 mounted on the axle 104, and vane blades 108 attached at a proximal end to the hub 106. Typically, the airlock 102 is provided with a plurality of vane blades 108. Bulk material conveying areas are typically defined between at least a pair of adjacent vane blades 108, an exterior surface of the hub 106 disposed between the proximal ends of the vane blades 108, an interior surface of the housing 105 extending between the distal ends of the vane blades 108, and side portions of the housing 105 adjacent the lateral edges of the vane blades 108.
In use, bulk material enters an airlock material inlet 112 and fills exposed bulk material conveying area(s). The rotor 103 continues to rotate about the axis 107 until the lateral sides of the bulk material conveying area(s) are registered with the an air inlet 124 and an air outlet 128 defined by the discharge apparatus 120. An airstream 130 passes through an inlet conduit 122 and an air inlet 124 defined by the inlet conduit 122 in fluid communication with an aperture formed in a side of the housing 105. The airstream 130 is directed by the air inlet 124 in a direction substantially parallel to the axis 107 and directly into one or more bulk material conveying area(s) from a lateral side of the bulk material conveying area(s). The bulk material is then entrained with the airstream 130 and thereafter discharged through an air outlet 128 defined by an outlet conduit 126 in fluid communication with an aperture formed in the opposite side of the housing 105. The bulk material is discharged with the airstream 130 through the outlet conduit 126 until it is distributed to the surrounding environment.
The airlock discharge assembly 100 has the benefit of providing a high level of cross-sectional area control, allowing the use of high velocities with a minimal amount of air flow. However, the end portions of the bulk material conveying areas must be kept open since the airstream 130 is required to laterally pass through the bulk material conveying areas. This arrangement typically causes sealing problems between the discharge apparatus 120 and the airlock 102. In addition, the vane blades 108 of the rotor 103 are exposed to high stresses when shearing objects lodged in the air inlet 124 more frequently in the air outlet 128, and at the edge of the material inlet 112. The airlock discharge assembly 100 also experiences excessive wear at the air outlet 128 as entrained bulk material traveling at a high velocity interferes with the housing 105 and other portions of the airlock discharge assembly 100.
FIG. 2 illustrates another conventional airlock discharge assembly 200 wherein an air inlet 224 directs an inlet airstream 230 below a conventional airlock 202, rather than directly through a side of the housing 205 and a lateral side of the bulk material conveying areas as with the airlock discharge assembly 100. The airlock 202 comprises rotor 203 including an axle 204 having an axis 207, a hub 206 mounted on the axle 204, and a plurality of vane blades 208 radially extending from an exterior surface of the hub 206. Bulk receiving areas may be defined between two adjacent vane blades 208, a portion of the outer surface of the hub 206 disposed between proximal ends of the vane blades 208, side portions of the housing 205 adjacent the lateral edges of the vane blades 208, and a portion of the interior surface of the housing 205 extending between the distal ends of the vane blades 208.
In use, bulk material enters through an airlock material inlet 212 and is received by exposed bulk material conveying area(s). As shown in FIG. 2, an airlock material outlet 210 is positioned below a bottom edge position 209 of the vane blades 208. As the bulk material conveying areas register with the airlock material outlet 210, the bulk material falls out of the registered conveying areas and is entrained with the airstream 230. FIG. 2 further illustrates a conventional discharge apparatus 220 extending below the airlock 202. In particular, an intermediate conduit 225 extends below and is attached to the airlock 202. The airstream 230 passes through an inlet conduit 222 and through an air inlet 224. The air inlet 224 directs the airstream 230 in a direction substantially parallel with the axis 207 of the axle 204. The air inlet 224 does not direct the inlet airstream 230 into the airlock material outlet 210 and also does not direct the inlet airstream 230 in a direction toward an area (e.g., a bulk receiving area) defined by the airlock 202. At most, after the airstream 230 passes through the air inlet 224, a portion of the inlet airstream 230 may defuse up into the airlock material outlet 210 wherein bulk material is entrained in the airstream 230, after which the airstream 230 directs the material through the air outlet 228 and into the outlet conduit 226 for discharging.
However, material tends to accumulate in stagnant spaces of the airlock discharge assembly 200 in use. Material also tends to accumulate between the air inlet and outlet, particularly at a point approximately ⅔ of the overall length from the air inlet 224. Material build up of this manner is discussed in xe2x80x9cPressure Drop Across a Pneumatic Conveying Feeding Teexe2x80x9d, Pneumatic Conveying, by H. H. Ottermann and S. J. Meijers, Vol.5, No.1, (March, 1993) pp.27-30.
FIG. 3 illustrates yet another conventional airlock discharge assembly 300 including an airlock 302 having a rotor 303. The rotor 303 comprises an axle 304 with an axis 307. A hub 306 is mounted to the axle 304 for rotation therewith and vane blades 308 are attached to an outer surface of the hub 306 and extend radially therefrom. Bulk material areas are defined between adjacent vane blades 308, a portion of the outer surface of the hub 306 extending between proximate ends of the blade vanes 308, an interior surface of the housing 305 extending between distal ends of the vane blades 308 and side portions of the housing 305 extending between lateral sides of the vanes 308. As further shown in FIG. 3, a conventional discharge apparatus 320 is provided for discharging bulk material from the bulk material conveying areas. As also shown in FIG. 3, an air inlet 324 is provided in a side wall of the housing 305 allowing an airstream 330 to be directly injected into the bulk material conveying areas between the vane blades 308 similar to the embodiment described previously in FIG. 1.
In use, bulk material enters the airlock discharge assembly 300 through an airlock material inlet 312 and is received into exposed bulk material conveying area(s). The rotor 303 continues to rotate until the bulk material conveying area(s) are registered with the air inlet 324 and the air outlet 328. An air inlet stream 330 passes through the inlet conduit 322 attached to the sidewall of the housing 305 and is directed substantially parallel to the axis 307 of the axle 304 and directly into one or more bulk material conveying area(s) from a lateral side of the bulk material conveying area(s). Bulk material is entrained into the airstream 330 and then exits through an air outlet 328 provided in a bottom wall of the housing 305. It is also known to install a circular knife at the air outlet 328 for wear resistance. The bulk material is then discharged with the airstream 330 through an outlet conduit 326.
The arrangement of components in the airlock discharge assembly 300, however, still causes high stress in the vane blades 308 when objects become lodged in the air outlet 328. Moreover, uneven wear of the vane blades 308 at the distal ends occur. Higher blade wear is typical at the distal ends of the vane blades 308 which pass over the air outlet 328.
Accordingly, it is an object of the present invention to obviate problems and shortcomings of conventional airlock discharge assemblies. More particularly, it is an object of the present invention to provide airlock discharge assemblies capable of discharging bulk material from an airlock.
Other objects of the invention are to reduce wear and friction on an airlock discharge assembly, and/or to maximize air velocities so that the airflow may impart energy more efficiently to bulk material in an airlock discharge assembly for any given amount of airflow.
Another object of the invention is to provide an airlock discharge assembly adapted to substantially prevent accumulation of portions of bulk material as the material is conveyed through the airlock discharge assembly.
To achieve the foregoing and other objects in accordance with the present invention, discharge apparatus are provided in order to connect to and cover an airlock material outlet. The discharge apparatus include an air inlet adapted to at least substantially direct an airstream through an airlock material outlet and toward an interior area defined by the airlock. The discharge apparatus further include a material directing trough adapted to receive an airstream and bulk material entrained therein from the airlock, and an extension member adapted to at least partially define a path of an airstream.
To further achieve the foregoing and other objects and in accordance with the present invention, an airlock discharge assembly is provided and includes a rotary airlock. The rotary airlock includes a housing having a bulk material inlet and a bulk material outlet. The rotary airlock further includes a central axle within the housing and a plurality of vanes extending in a direction generally away from the central axle wherein adjacent vanes define bulk material conveying areas within the housing. An air inlet is in communication with the housing and is adapted to at least substantially direct an airstream in a direction nonparallel to the axle and toward a bulk material conveying area in communication with the bulk material outlet.